This Phase 2, flexible-dosage, single-blind study consists of a Screening Phase (up to 28 days [Visit 1]), a 5-week Treatment Phase (1 week of treatment with placebo [Baseline-1/Visit 2 to Baseline-2/Visit 3] followed by 4 weeks of treatment with EB-1020 SR [Weeks 1 through 4/Visits 4 through 7]), and a 2-week Discontinuation Phase, which starts at the time of Week 4/Visit 7 and includes a Follow-up Visit (Week 6/Visit 7). Approximately 40 patients are planned to enter the treatment period. At Baseline-1, patients must have a score of greater than or equal to 28 on the ADHD-RS-IV to be eligible to continue participation in the study. At the end of single-blind placebo treatment (i.e., Baseline-2), the ADHD-RS-IV with adult prompts is re-administered. Patients who show an improvement greater than or equal to 30% over baseline values or who have a score of less than 28 on the ADHD-RS-IV are withdrawn from the study prior to receiving any active drug. Those who show less than 30% improvement from Baseline-1 to Baseline-2 scores will continue in the study. The consent form will be phrased such that patients are not informed of the exact timing of EB-1020 SR vs. placebo treatment in order to maintain the blinded nature of the placebo treatment and reduce potential placebo effects. Dosing will be flexible, with a target maximum dosage of 500 mg daily in divided doses (morning and afternoon, approximately 5 hours later) to be achieved if possible during Week 2 of EB-1020 SR treatment. The patient will take a starting dose of 100 mg of EB-1020 SR daily; the dose will be titrated in 100 mg increments up to the maximum dosage of 500 mg daily. The treating physician will escalate the dose to the maximum dose if patients have not achieved remission of ADHD in his/her judgment, and EB-1020 SR is still well tolerated. If in the physician's judgment the patient could not tolerate further dose escalation, or is not tolerating the current dose well, the dose may be maintained or reduced, with the goal of re-assessing dose and response at the subsequent visit for a possible increase in dose, until study completion.